Investigation of structure and composition of buried oxide layers formed by oxygen-ion implantation into silicon

Abstract

Single-crystal ⟨ 1 1 1 ⟩ silicon samples were implanted at room temperature and at elevated temperature (325 °C) with oxygen (16O+) ions at 140 keV energy to fluence levels 1.0×1017, 2.5×1017 and 5.0×1017 cm−2 to synthesize buried layers using the SIMOX (separation by implanted oxygen) process. We have studied the process of buried oxide formation as a function of implantation temperature and fluence. The effects of fluence and implantation temperature on the structure and composition of the ion-beam-synthesized, buried silicon oxide layers were investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) studies and Rutherford backscattering spectroscopy (RBS) measurements, respectively. The FTIR spectra of the implanted samples revealed a single broad absorption band in the wavenumber range 1250–750 cm−1, indicating the formation of silicon oxide. The integrated absorption band intensity was found to increase with increasing ion fluence. The absorption peak of the elevated-temperature-implanted sample was broader than that of the room-temperature-implanted sample. The structure of the ion-beam-synthesized oxide layers showed strong dependence on the fluence and implant temperature. The XRD studies reveal the synthesis of silicon oxide (SiO2) structure at all fluences. The RBS measurements show that the thickness of the buried oxide layer increases with an increase in the oxygen fluence. In general, however, the thickness of the top silicon layer was found to decrease with an increase in the ion fluence.